Light curing devices in which the heat generated by the light source is dissipated using heat sinks, which are generally supplied by a fan, have been known for a long time. DE-U 81 35 468 thus exhibits a dental photopolymerization device in which a heat sink is intended to dissipate heat that is produced there. The heat sink is located in the cooling air stream of a cooling fan.
Light curing devices which operate with extremely high power have recently been disclosed. The power is generated either by LEDs or by laser diodes and is used to polymerize the dental restoration part, typically in the patient's mouth in the case of hand-held devices.
One example of such a light curing device which operates using a laser diode can be gathered from DE 37 19 561. In this solution, a heat sink having cooling ribs is fitted to the laser diode such that it is thermally conductively connected to the latter. The control electronics are held in a separate box which is protected from dust and is at a considerable distance from the heat sink.
Furthermore, DE 102 14 366 A1 by the present applicant has disclosed the practice of implementing a printed circuit to the side of a heat sink in slots which are provided between cooling ribs. This practically stops operation of the relevant cooling ribs, which is unfavorable for the relationship between cooling effect and weight.
Furthermore, the use of so-called heat pipes has also been proposed. Such heat pipes have been known for a relatively long time and are used to pass heat which has been generated at one location to a remote location and to dissipate it there. However, such solutions have proved to be rather unwieldy for light curing devices in the form of hand-held devices.
Light curing devices—especially in the form of hand-held devices—must be particularly compact. Heat sinks which are supplied with a cooling air stream, which is generated using a fan, are therefore frequently used in order to dissipate the heat generated by the light source. On the other hand, the cooling air stream must not blow out in the region of the light source, that is to say at the front of the light curing device, since otherwise the patient and the treatment site would be adversely affected by the emerging cooling air stream.
If there is a small cross section available for the cooling air stream, the fan must build up a correspondingly increased amount of pressure for the heat exchange in order to provide the desired cooling air stream for overcoming the flow resistances. It is known that a fan allows a pressure difference of at most one bar to be provided in the suction mode, this value also being able to be achieved only in theory.
Therefore, it is necessary to implement a fan in the delivery mode in order to provide a greater pressure difference.
If the direction of flow of a cooling stream in a light curing device were then desired from the front to the rear, the fan would have to be arranged, in this respect, in the front region of the light curing device if it were intended to operate in the delivery mode. On the other hand, this is not compatible with the implementation of the light source at this location.
Components which likewise have to be accommodated in the light curing device are required to electrically drive the light source. Since the heat sink-apart from the rechargeable batteries—is the heaviest component in the light curing device, it is necessary to arrange the components in a balanced manner, in which case the practice of accommodating the components in the handle of the light curing device has also already been disclosed.